1996 Johnson Evinrude "ED" 9.9 thru 30 2-Cylinder Service Manual, P/N 507122, Page 312Get this manual
Description of Charging System The outboard charging system consists of battery, flywheel, an alternator stator, and rectifierThe engine's battery can affect the charging system operationThe battery should be of heavy-duty marine construction, should be the correct capacity for the application, and should be in good condition with normal charge
The engine's flywheel contains the permanently charged magnets which provide the energy to power the stator windingsThe magnets must be at their original design strength for full alternator outputThe alternator stator consists of many windings of wire wrapped around metal laminationsThe stator is attached to the ignition plateThe flywheel's magnetic lines of force cutting through the stator windings produce alternating currentThe stator or its leads could be damaged which could result in reduced or no alternator outputThe rectifier consists of series of diodes, built into metal case, which changes the stator's alternating current to the direct current used to charge the batteryOne, several, or all of the rectifier diodes might become damaged, resulting in system grounded condition, no charge condition, or an incorrect charging rate